Date: Fri, 6 Dec 2019 16:22:21 +0200 From: Konstantin Belousov <kostikbel@gmail.com> To: "O'Connor, Daniel" <darius@dons.net.au> Cc: freebsd-stable <freebsd-stable@freebsd.org> Subject: Re: Disabling speculative execution mitigations Message-ID: <20191206142221.GL2744@kib.kiev.ua> In-Reply-To: <C19DE24E-22CB-4E55-95CE-0A07FC8A23F5@dons.net.au> References: <C19DE24E-22CB-4E55-95CE-0A07FC8A23F5@dons.net.au>
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On Fri, Dec 06, 2019 at 03:51:04PM +1030, O'Connor, Daniel wrote: > Hi, > I am trying to track down a performance drop with the ASPEED xorg video driver between FreeBSD 11 and 12 (I'm not expecting miracles from it but it was basically unusable..) > > I wondered if some of the speculative execution mitigations could be causing the problem so I did some digging and found these.. > > vm.pmap.pti="0" # Disable page table isolation > hw.ibrs_disable="1" # Disable Indirect Branch Restricted Speculation This line enables IBRS. > hw.mds_disable="0" # Disable Microarchitectural Data Sampling flush > hw.vmm.vmx="1" # Don't flush RSB on vmexit (presumably only affects bhyve etc) I have no idea what this line should configure. > hw.lazy_fpu_switch="1" # Lazily flush FPU > > Does anyone know of any others? Did you read security(7) (on HEAD)? > > I have 2 systems with the same motherboard (Supermicro X11SSH-F), one is older and runs FreeBSD 11 (and had an older BIOS_ and the newer runs FreeBSD 12. > > FWIW on FreeBSD 11 the performance (measured by a subset of x11perf benchmarks) went down 40% after updating to the latest BIOS (2.2a). Unfortunately on FreeBSD 12 rolling back to the original BIOS (2.2) did not improve performance. > > -- > Daniel O'Connor > "The nice thing about standards is that there > are so many of them to choose from." > -- Andrew Tanenbaum > > > _______________________________________________ > freebsd-stable@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-stable > To unsubscribe, send any mail to "freebsd-stable-unsubscribe@freebsd.org"
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